What limits should be established prior to every scuba dive?

Establishing limits prior to every scuba dive is crucial for safety and effective dive planning. The correct answer encompasses multiple important factors: maximum bottom time, maximum depth, and minimum air pressure.

Maximum bottom time helps to manage exposure to pressure and avoid decompression sickness, as staying too long at depths increases the need for careful ascent and potential stops. Maximum depth is critical because it relates to the physiological limits of the diver, particularly in relation to nitrogen absorption and the risks associated with deeper dives, such as impaired air supply or increased pressure effects. Finally, specifying a minimum air pressure before a descent ensures that divers have a sufficient air supply for the entire planned dive, as well as a safe ascent, which includes decompression stops if required.

This comprehensive approach ensures that divers are aware of and can adhere to safety practices, thus reducing the risks associated with diving. The other options fail to provide such a holistic safety framework, focusing narrowly on only one aspect of dive planning.